Modern disc drives are commonly used in a multitude of computer environments ranging from super computers through notebook computers to store large amounts of data in a form that can be made readily available to a user. Typically, a disc drive has one or more magnetic discs that are rotated by a spindle motor at a constant high speed. Each disc surface has a data recording surface divided into a series of generally concentric data tracks radially spaced across a band having an inner diameter and an outer diameter.
The data is stored within the data tracks on the disc in the form of magnetic flux transitions. The flux transitions are induced by an array of read/write heads. Typically, each data track is divided into a number of data sectors that store fixed sized data blocks.
The read/write head includes an interactive element such as a magnetic transducer that senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, to write data to the disc surface, the read/write head transmits an electrically induced, short duration magnetic field that induces magnetic transitions on the selected data track.
Each read/write head is mounted to a load arm. Each load arm is supported by an actuator arm that is typically one of a plurality of members extending from an actuator cartridge-bearing member of an actuator assembly. The actuator assembly provides the rotary motion needed to selectively position the read/write head over a selected data track of the disc to either read data from or write data to the selected data track. The read/write head includes a slider assembly having an air-bearing surface that responds to an air bearing developed by the interaction of the read/write heads with a boundary layer of air. The boundary layer of air is developed by the rotation of the discs beneath the read/write heads. In response to the air bearing the read/write head flies adjacent the disc surface at a desired height thereby creating a gap between the read/write head and the surface of the corresponding disc.
Typically, a plurality of open-center discs and spacer rings are alternately stacked on a hub of the spindle motor. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings, clamp ring and spindle motor hub define a disc pack. The read/write heads attached to the actuator assembly accesses the surfaces of the stacked discs.
In addition to the read/write heads the actuator assembly generally includes head wires, which conduct electrical signals from the read/write heads to a flex circuit that, in turn, conducts the electrical signals to a read channel located on the printed circuit board (PCB) of the disc drive. Normally the electrical signal paths are routed through one or more connectors en route to the read/write channel. The connectors facilitate the electrical connection between the flex circuit of the disc drive and the PCB of the disc drive. However in so doing, the contacts of the connectors typically induce an added inductance and capacitance into the circuit thereby causing a change in inductance and capacitance per unit length along the signal path. This change in inductance per unit length along the signal path frequently results in a parasitic electrical degradation of the signal. Several approaches have been used to accommodate the data signal interconnect needs of a disc drive, but in general, these approaches have been silent regarding resolution of parasitic electrical signal degradation problems caused by changes in inductance per unit length along the signal path.
In connecting the flex circuit and the PCB one previous approach makes use of an apparatus with a three connector combination configuration having a flex circuit component; a pass-through connector; and a printed circuit board connector. Under this scheme, the first primary component, the flex circuit connector (the connector body housing female connector pins), is soldered directly to the flex circuit. The second primary component, the pass-through connector having a connector body that houses male pins with a top portion protruding from a top side of the connector body and a bottom portion protruding from a bottom side of the connector body, is disposed adjacent the basedeck with the bottom portions of the male pins extending from an aperture or slot in the basedeck. The third primary component, the printed circuit board connector with a connector body housing female connector pins, is soldered directly onto the PCB. This approach has the advantage of confining the flex circuit internal to the HDA.
Under this three-connector combination approach the flex circuit connector is mounted to a flex circuit mounting bracket. Then the flex circuit connector connects to the pass-through connector internal to the HDA. Contact between the flex circuit connector and the pass-through connector is maintained by physically securing the flex circuit mounting bracket and the pass-through connector to the basedeck of the disc drive. External to the basedeck the pass-through connector connects to the printed circuit board connector. The printed circuit board connector is mounted to the PCB of the disc drive, and the PCB is then fastened to the basedeck of the disc drive. Attaching the disc drive PCB to the basedeck provides the means of maintaining physical contact between the pass-through connector and the printed circuit board connector.
Another approach of connecting a flex circuit to the disc drive PCB is to feed the flex circuit external to the HDA. Under this approach the flex circuit typically passes between the basedeck and a gasket mounted on the cover of the disc drive. Once the flex circuit is external to the HDA, the flex circuit commonly mates with an edge connector that is soldered to the PCB of the disc drive. The disadvantages of this external feed approach are exposure of the flex circuit to handling damage during the assembly process; customer installations, and in automated production processes. The production difficulties tend to arise when trying to locate, secure and connect the non-rigid flex circuit via automated means.
Normally, under this external feed approach, a flex circuit alignment member is secured directly to the flex circuit and a printed circuit board connector (a connector body housing female connector pins) is soldered directly to the PCB. The flex circuit is secured to an alignment member which lends support to the flex circuit and provides a means to maintain registration of the contact pads of the flex circuit in relation to the female connector pins or contact pads of the PCB. Additionally, the flex circuit is connected to the PCB external to the basedeck thereby exposing the flex circuit to potential damage. The PCB is then fastened to the disc drive basedeck to maintain stability of the connection. An example of an adaptation of this approach is disclosed by U.S. Pat. No. 5,403,202 to Donald P. Roehling ("Roehling '202").
As is known, key factors that influence the choice of an interconnection solution to facilitate connection between the flex circuit and the disc drive PCB are quality; space constraints; mass production requirements; component costs; and component performance (for both mechanical and electrical characteristics). In historical perspective, with technology advances in the disc drive industry, one or more factors have dominated the decision process when electing an interconnection solution for a specific disc drive technology advancement. It is evident that the prominent key factor driving the signal interconnection technology invention in Roehling '202 was the space constraint challenges presented by disc drives.
In contrast to the Roehling '202 approach, the three-connector combination approach was driven by the desire to minimize the exposure of the flex circuit to handling and use damage while maximizing the interconnect configuration for automation. Under the three-connector combination approach the flex circuit is confined internal to the HDA of the disc drive, resolving the problem of exposing the flex circuit to handling and environmental damage, while use of the pass-through male pinned connector promotes ease of production.
Advancements in bit transfer rate technologies, with transfer rates in the range of one gigabit per second and the resultant pico-second range rise and fall signal time, have driven the interconnection electrical performance characteristics of the connection itself to be a key factor of read/write signal management. As bit transfer rates rise, negative effects on the integrity of the read/write signal, primarily parasitic electrical signal degradation due to changes in inductance per unit length along the signal path, begin to dominate as the key electrical performance factor to be addressed by read/write signal interconnection technology. As transfer rates approach the gigabit per second range, maintaining uniform inductance along the signal becomes the dominant key factor.
The signal management burdens within read/write signal interconnection technology, brought about by the emergence of transfer rates in the gigabit per second range, coupled with the remaining key factors of quality, mechanical performance, space constraints, automation considerations and component costs, have collectively converged to generate an unmet need in the industry for an improved flex-to-PCB connector that minimizes the parasitic electrical signal degradation effects created by changes in inductance per unit length seen by the read/write signal along the signal path.